HRP20050063A2 - Micro-cellular or non-cellular light-stable polyurethane material and method for the production thereof - Google Patents

Description

The presented invention relates to a process for the production of microcellular or non-cellular photostable polyurethane material with a density greater than 500 kg/m3, preferably greater than 700 kg/m3, a process in which the reactive mixture is left to react to obtain a polyurethane material, where the reactive mixture consists of components that are defined in the preamble of claim 1 and which specifically contains a catalyst component, which essentially does not contain lead and which contains organobismuth (III) as a catalyst.

Such a process is used for the production of thermoplastic polyurethane material (TPU), choosing the functionality of two different, mutually reactive components. TPU material is produced, for example, in the so-called reactive extrusion process, in the form of granules that are intended for further processing by extrusion or by the process of forming lubricants. Non-thermoplastic polyurethane materials are usually produced by a spray or reactive injection molding (REVI) process.

A spray process for the production of a photostable elastomeric polyurethane material, which is microcellular or noncellular, is described, for example, in EP-B-0 379 246. In this European patent, various types of catalysts are described, including organolead, organobismuth, organotin and alkali catalysts, which are used in combination with an amine initiator to achieve the desired catalytic effect. To improve the desired photostability of the polyurethane material, mixtures of antioxidants and UV absorbers have been described. Numerous examples of different polyurethane formulations are described, each of which uses the same combination of antioxidants and UV absorbers.

A RIM process for the production of photostable microcellular or acellular elastomeric polyurethane material is described in EP-B-0 929 586.1 in the processes described in this patent, various types of catalysts are described including organolead, organobismuth, organotin and alkali catalysts. These catalysts are used in combination with an amine initiator to achieve the desired catalytic effect.

Polyurethane materials, made in accordance with the European patents described above, are used mainly in the automotive industry, for example, for sealing windows, and especially for interior decorative parts, such as dashboards, consoles, glove boxes, door trims, etc. For this purpose, always high demands are placed on polyurethane materials. First of all, any use of organools is prohibited or will be prohibited in the near future. In addition, while initially only the material's fogging properties were observed (measured in accordance with DIN 75 201, determination of windshield fogging properties of sealing materials in motor vehicles), now the content of volatile organic compounds (VOC) will also be determined. Daimler Chrvsler, for example, developed its test procedure PB VWT 709 for measuring the VOC content of a polyurethane sample, while Volkswagen developed its own test procedure PV 3341, the first edition of which was as late as December 1987. In this specification, VOC values are always measured according to the Daimler Chrysler test procedure, PB VWT 709.

An important limitation of the processes shown in the European patents described above, especially those processes where no lead catalyst was used, is that they produce polyurethane materials with an excessively high VOC value. Now the inventors have found that this is primarily due to the use of organobismuth, organotins and alkaline catalysts (especially DBU compounds: 1,8-diazobicyclo(5,4,0)undecene-7-phenolate).

The next compound that has a negative effect on the VOC value is BHT (bis-2,6-tert butyl-4-hydroxytoluene), which is used as a stabilizer (antioxidant) in components containing active hydrogen, used in the examples from EP-B-0 379 246 and EP-B-0 929 586. Since the late 1990s, polyol manufacturers have started producing BHT-free polyether polyols, i.e., containing less than 50 ppm BHT. When such BHT-free polyol is used in the examples of EP-B-0 929 586, where there are no organool compounds as catalysts, the VOC values in these examples are still too high, namely significantly more than 250 ppm. These high VOC values originate from the presence of the organotin catalyst and the organobismuth and/or alkali catalyst, which were used in these examples and which the present inventors have found to increase the VOC values many times more than the organolead catalyst.

The aim of this invention is, therefore, to provide a new process for the production of microcellular or non-cellular photostable polyurethane material, which allows to obtain a polyurethane material with a VOC value of less than 250 ppm, or even less than 150 or 100 ppm, without the use of an organolead catalyst.

To achieve this goal, a characteristic of the process according to the present invention is that the organobismuth catalyst contains at least one organobismuth (III) catalyst corresponding to the following formula (I):

[image]

where m = 0 -2

p = 1-3

m + p = 3

R1 is a C1-C8 alkyl group, a

R2 is either

a linear or branched C13-C19 alkyl or alkenyl group, or

a linear or branched C1-C19 alkyl or alkenyl group, preferably a C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups, and/or

said catalyst component contains, in addition to said organobismuth catalyst, at least one organotin (II or IV) catalyst, to which the following formula (II) corresponds:

[image]

the following formula (III):

[image]

or the following formula (IV):

[image]

where is

R1 C1-C8 alkyl group; And

R2 is or

a linear or branched C13-C19 alkyl or alkenyl group, or

a linear or branched C1-C19 alkyl or alkenyl group, preferably a C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups,

where the components of the reactive mixture are further selected in such a way that the obtained polyurethane material has a VOC value, measured in accordance with the Daimler Chrvsler PB VWT 709 standard, lower than 250 ppm, preferably lower than 150 ppm and most preferably lower than or equal to 100 ppm.

In accordance with the present invention, it has been found that the use of such organobismuth and/or organotin catalysts achieves a substantial reduction in VOC values without the use of an organolead catalyst. The term "substantially free of lead" is used in this specification to mean that lead is not present or is present only in traces not particularly detectable by conventional techniques, the polyurethane material containing less than 5 ppm, preferably less than 1 ppm of the element of lead.

For the production of polyurethane foams, which have a density of less than 500 kg/m3, it is already known from US-B-6 194 475 that zinc (II) or tin (II) ricinoleate is used in combination with stano caprylate as a catalyst to reduce the release caprylic acid. In one example, namely, Example 19, tin (II) ricinoleate was used as the sole catalyst. From this example it appears that even when using an amount of stannous ricinoleate that is five times the amount of stannous octoate, the time to complete foaming is still 15% longer. The need for a higher amount of tin (II) ricinoleate as a catalyst in the production of flexible polyurethane foam, compared to tin (II) octoate, is confirmed in US-A1-2002/0016376.

In the process according to the present invention, however, a microcellular or non-cellular polyurethane material is made which has a higher density and cures in a much shorter time. The polyurethane material is further based on an isocyanate compound, where the isocyanate groups are not directly attached to the aromatic group and which is therefore much less reactive than the aromatic isocyanates used in US-B-6 194 475 and US-A1-2002/0016376. In other words, the catalytic system used in the process according to the present invention is more efficient to avoid the need for an excessive amount of catalyst. Such a large amount of catalyst should be avoided not only from an economic point of view. The maximum amount of catalyst in a polyol or isocyanate mixture is, for example, also limited by the compatibility of the various compounds within the mixture. When the compounds are not compatible with each other in their respective amounts, unfavorable phase separations within the mixture may occur, for example.

In contrast to the processes described in US-B-6 194 475 and US-A1-2002/00163 76, the process of this invention uses an organobismuth catalyst, which has been found to be significantly more effective in catalyzing "non-aromatic" polyurethane formulations than organotin or an organozinc catalyst.

In relation to the organobismuth catalyst, the present inventors rather unexpectedly found that, in contrast to the use of an organotin (II) catalyst in the production of aromatic polyurethane foam, the same catalytic effect is achieved when bismuth octoate (=bismuth caprylate) is substituted, which is a common organobismuth catalyst in the production of microcellular or non-cellular photostable polyurethane materials, with a similar amount of bismutholeate, i.e., an amount of bismutholeate containing a similar amount of the bismuth element as bismuth octoate.

The present inventors have further found that, for both organobismuth and organotin catalysts, high molecular weight carboxylates, other than ricinoleate, and lower molecular weight carboxylates, containing isocyanate reactive groups, are effective in reducing volatilization of the polyurethane material, which is in contrast to findings in US-B-6 194 475, according to which zinc stearate, oleate and 12-hydroxystearate would not have any positive effects on evaporation values.

Regarding the use of organotin catalyst, the combination of organobismuth and organotin catalyst was found to be advantageous in light of the fact that the organobismuth catalyst causes a rapid initial increase in viscosity while the organotin catalyst is more active at the end of the polymerization reaction. Since a very rapid increase in viscosity has a negative effect on the tack-free time, this tack-free time is reduced by replacing part of the bismuth catalyst with a tin catalyst. Such a reduced curing time is important to achieve an economically acceptable molding time.

In one advantageous embodiment of the process according to the present invention, the catalyst component further contains an organozinc (II) catalyst corresponding specifically to the following formula (V):

[image]

where R2 is a C1-C19, preferably C1-C12, alkyl or alkenyl group, which is linear or branched and which is substituted or unsubstituted. Advantageously, the organozinc catalyst comprises zinc dioctoate.

The present inventors have found that, just like the organolead carboxylates, the zinc carboxylates cause no volatilization or only a small amount. For the production of microcellular or acellular photostable polyurethane materials, the combination of an organobismuth and an organozinc catalyst has been found to be advantageous in light of the fact that the organozinc catalyst competes with or inhibits the organobismuth catalyst, thus preventing the organobismuth catalyst from increasing too rapidly in viscosity, so that the activity of the organobismuth catalyst is extended and the curing time is shortened.

It is advantageous for the catalyst component to contain organobismuth, organozinc and organotin as catalysts, especially when the reactive mixture is applied by spray. In this way, the activity of the bismuth catalyst is extended by competing with the zinc catalyst and the organotin catalyst ensures effective curing at the end of the polymerization reaction. This second effect is particularly favorable in the application of spray due to the lower curing temperature of the polyurethane material at the end of the polymerization reaction, and therefore its lower reactivity, compared to the RIM process that takes place in a closed, heated mold.

Other specificities and advantages of this invention will become clear from the following description of the series of components and formulations used in the processes of this invention and polyurethane materials obtained from it.

In general, the invention relates to a process for the production of microcellular or non-cellular photostable polyurethane material, specifically, elastomeric polyurethane material, which has a density greater than 500 kg/m3, in particular, greater than 700 kg/m3. In practice, the density of polyurethane material is usually less than 1200 kg/m3. Polyurethane materials are microcellular, preferably with an integral coating, or non-cellular. They are produced starting from a reactive mixture of polyurethane precursors, which are left to react, in particular, by the so-called "single injection" process, where the components of the reactive polyurethane mixture are mixed before being placed in the mold or on the surface of the mold. This is done by a spray process, as described in the example in EP-B-0 379 246 or by a reaction injection molding (RIM) process, as described in the example in EP-B-0 929 586. In these two different processes, two mixtures are usually made up first, namely the so-called polyol mixture and the isocyanate mixture, which are mixed together before being sprayed onto the surface of the mold or injected into the mold. In addition to possible applications in spray or RIM, thermoplastic polyurethane material is also made, for example, by the reactive extrusion technique.

In the process of this invention, the reactive polyurethane mixture consists of at least the following components:

A) isocyanate component composed of at least one isocyanate compound that has at least two NCO groups that are not directly connected to an aromatic group;

B) components that are reactive with the isocyanate they contain

b1) component with active hydrogen, which has at least one compound with active hydrogen and has:

functional groups containing primary and/or secondary OH-groups, NH-groups and/or

NH2- groups;

nominal functionality from 2 to 8; and

equivalent weight between 100 and 4000, preferably between 800 and 2000;

b2) from about 0 to about 30 parts, preferably from about 2 to about 30 parts, per 100 parts of components b1, b2 and b3, chain-extending and/or cross-linking components, consisting of at least one chain-extending component and/or at least one component that cross-links them, with an equivalent weight of less than 100, whose functional groups are OH- groups, of which at least 50% are primary OH- groups and whose functionality is from 2 to 6; and

b3) an amine-initiator component that forms a co-catalytic system with the catalyst component C and that consists of at least one amine initiator with a functionality of 2 to 6 and an equivalent weight of less than or equal to 200 and that contains at least one aliphatic or alicyclic NH2- or NH - group; and

C) a catalyst component that is essentially lead-free and that contains at least one organobismuth (III) catalyst.

The isocyanate component contains one isocyanate compound or a mixture of isocyanate compounds. The preferred isocyanate compounds are very different. An essential feature of isocyanate compounds is that they contain at least two NCO groups that are not directly connected to an aromatic group. The polyurethane material obtained in this way is made photostable. The isocyanate component advantageously contains IPDI (isophorone diisocyanate) monomers or trimers or their mixture, where it is advantageous that the IPDI monomer/trimer mixture has an NCO content between 24.5 and 34% by weight. Optionally, an isocyanate prepolymer is also used, where a part of the NCO groups has already reacted with a compound containing active hydrogen. Instead of IPDI, other "non-aromatic" isocyanates are used, such as TMXDI, HDI, H6XDI and H12MDI or their derivatives. These isocyanates are described in EP-B-0 379 246, the disclosure of which is incorporated herein by reference.

Isocyanate-reactive components primarily contain an active hydrogen component. This component consists of one or more compounds containing active hydrogen, which have an equivalent weight between 100 and 4000 and a nominal functionality of 2 to 8. Advantageously, these compounds containing active hydrogen are polyether polyols with terminal OH-groups, obtained by polyaddition of propylene oxide and/or ethylene oxide on low molecular weight initiators with OH-, NH- and/or NH2- groups and with functionality from 2 to 8.

This functionality corresponds to the nominal functionality of polyether polyols. Favorable nominal functionality of compounds containing active hydrogen is from 2 to 4. Regarding the reactivity of compounds containing active hydrogen, it is favorable that at least 50%, and even more favorable at least 70% of OH- groups reactive with isocyanate are primary OH- groups.

Instead of, or in addition to the OH- group, compounds containing active hydrogen also contain NH- or NH2-groups reactive with isocyanate. An example of such compounds are the so-called Jeffamines from Texaco.

Other types of compounds containing active hydrogen are polyester polyols which form ester products by condensation of dicarboxylic acid with polyalcohols of low molecular weight, with functionality from 2 to 8, preferably from 2 to 4, which correspond to the nominal functionality of polyester polyols.

Other advantageous compounds containing active hydrogen are polytetramethylene ether glycols (PTMG), which are polytetrahydrofuran with 100% primary OH- groups and which have a nominal functionality of 2 and a hydroxyl number of 35 to 200.

The isocyanate-reactive components further comprise a chain-crosslinking and/or chain-extending component, consisting of at least one chain-extending component and/or at least one chain-crosslinking component, the functional groups of which are OH groups. The chain-extending and/or cross-linking component has an equivalent weight of less than 100. The presence of this chain-extending and/or cross-linking component is usually, but not always, necessary. It is used in an amount from 0 to about 30 parts, preferably from about 2 to about 30 parts, per 100 parts of components b1, b2 and b3.

Typical favorable components that crosslink or extend the chains only with active OH groups, with a functionality of 2 to 4, a hydroxyl number greater than 250 and a concentration of primary OH groups greater than 50%, are ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, glycerin, trimethylolpropane, triethanolamine, trimethylolethane, pentaerythritol, bisphenol A and cyclohexanedimethanol, and also possible addition products from all these examples with less than 5 or with 5 moles of ethylene oxide and/or propylene oxide per mole of the cross-linking or chain-extending component .

The isocyanate-reactive components finally contain an amine initiator component that forms a co-catalytic system with catalyst component C. Such initiators are described in US-A-4,150,206 and US-A-4,292,411, provided that the required minimum functionality of 2.

Aliphatic or alicyclic alkanolamines or polyamines, with an amino group not directly attached to the aromatic ring, are usually considered. The number of NH- and/or NH2- groups is at least 2, if OH- groups are not present and at least 1 if OH- groups are present. The total number of reactive groups, formed by -NH, -NH2 or -OH, generally varies between 2 and 5.

Typical preferred compounds, especially aliphatic compounds with a functionality of 2 to 4, are the following: monoethanolamine, diethanolamine, diisopropanolamines, ethylenediamine, isophoronediamine, N,N'-dimethyl(diethyl)-ethylenediamine, 2-amino-2-methyl (or ethyl)-1-propanol, 2-amino-1-butanol, 3-amino-1,2-propanediol, 2-amino-2-methyl (ethyl)-1,3-propanediol.

"Jeffamines" (Texaco) (propylene oxide addition products having mostly terminal primary NH2 or secondary NH groups - functionality 2 to 3). Addition products of propylene oxide and/or ethylene oxide to an ethylenediamine initiator (2 to 8 mol/mol ethylenediamine).

The aforementioned components of the photostable polyurethane formulation have already been described in more detail in EP-B-0 379 246 and also in EP-B-0 929 586, the descriptions of which are incorporated herein by reference.

The disadvantage of known photostable polyurethane formulations is that the produced polyurethane materials have a very high VOC value and that most of them are produced by a catalytic system containing an organolead catalyst.

To reduce the VOC value, components with active hydrogen are primarily used, especially polyether polyol, which does not contain BHT or which contains only a small amount of this stabilizer, especially an amount less than 50 ppm. BHT is known to actually contribute to the evaporation of polyurethane materials and should therefore be avoided to reduce the VOC value.

An essential property of this invention to reduce VOC evaporation values is the special choice of catalyst. In the process of this invention, an organobismuth (III) catalyst is used, optionally in combination with organotin (IV), organozinc (II) and/or some other catalyst such as a zeolite type catalyst. The alkaline catalysts described in EP-B-0 379 246 are, however, no longer used, or only in such a small amount that the VOC value of the obtained polyurethane material remains below the upper limit of 250, 150 or 100 ppm.

Organobismuth (III) catalyst

It is advantageous that the organobismuth catalyst used in the process of this invention contains an organobismuth catalyst corresponding to the following general formula (I):

[image]

where is

m = 0-2

p=1-3

m + p = 3

R1 is a C1-C8 alkyl group, a

R2 is either:

a linear or branched C13-C19 alkyl or alkenyl group, or

a linear or branched C1-C19 alkyl or alkenyl group, preferably a C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups.

In comparison with the organobismuth catalyst bismuth-(III)-2-ethylhexoate (= "bismuth octoate"), the organobismuth catalysts of formula (I) produce considerably less volatile compounds in the polyurethane material. This is either due to the fact that the carboxylic acid obtained when the catalyst is hydrolyzed is less volatile because it has a higher molecular weight, or due to the fact that this carboxylic acid is substituted with a group reactive with isocyanate, so that it is chemically bound in the polyurethane network.

When the bismuth catalyst is a mono- or dialkylcarboxylate (m = 1 or 2), it is advantageous if the alkyl group R1 is a C1-C4 alkyl group in view of higher reactivity and lower melting point. The lower melting point is important due to the fact that it is advantageous to add the catalyst in a liquid state to the polyurethane system. It is most favorable that the bismuth catalyst is bismuth carboxylate (m = 0), because such carboxylates are already commercially available and provide a good catalytic effect. Bismuth catalysts of this type are, for example, bismuth myristate, bismuth myristoleate, bismuth palmitate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth linolenate and bismuth ricinoleate.

Among these examples, bismuth ricinoleate contains a carboxyl group substituted with an isocyanate-reactive group, more specifically, an OH- group. In the case of such substituted carboxyl groups, the R2 group is of lower molecular weight. Preferably, the R2 group is a C7-C19 alkyl or alkenyl group.

Since groups reactive with isocyanate on the catalyst compound cause a decrease in catalytic activity by binding the catalyst to the polyurethane matrix, it is advantageous to use an organobismuth catalyst of formula (I), where R2 is a C13-C19 alkyl or alkenyl group that is not substituted by a group reactive with isocyanate. It is further advantageous that the R 2 group is linear.

It is advantageous for the R2 alkyl or alkenyl group to be a C15-C19 alkyl or alkenyl group, given the lower vapor pressure of higher molecular weight carboxylic acids resulting in lower VOC values. It is further advantageous for the R 2 groups to be alkenyl groups. The presence of one or more double bonds actually lowers the melting point of the catalyst so that, even with a higher molecular weight, the catalyst is added in liquid form to the polyurethane system. In view of the fact that they combine a relatively high molecular weight with a relatively low melting point, oleyl groups, linoleyl groups, linolenyl groups or combinations thereof are most advantageous as R 2 COO- groups in the formula (I) organobismuth catalyst. The most favorable organobismuth catalyst is bismuth (III) oleate, where a small part of the carboxylate groups consists of linoleate and linolenate groups due to the use of natural oils for the preparation of this organobismuth catalyst.

As mentioned earlier, the reactive mixture is first sprayed onto the surface of the mold. In this case, the organobismuth catalyst is usually used in such an amount that the resulting polyurethane material contains 150 to 850 ppm, preferably 150 to 600 ppm, of the element bismuth. The reactive mixture should also be injected into a closed mold, according to the reaction injection molding (RIM) process. In this case, the organobismuth catalyst is usually used in such an amount that the resulting polyurethane material contains 250 to 2500 ppm, preferably 800 to 1650 ppm, of the element bismuth.

In the process of this invention, it is advantageous that the organobismuth catalyst is added to the polyol mixture, because when it is added to the isocyanate mixture, a system is obtained that is less stable in relation to reactivity. When added to a polyol mixture, the organobismuth catalysts of formula (I), where R 2 is C 13 -C 19 , preferably a C 13 -C 19 alkyl or alkenyl group, provide the additional advantage of being less susceptible to hydrolysis in the polyol mixture.

In addition to organobismuth catalysts of formula (I), the organobismuth catalyst used in the process of this invention contains other organobismuth (III) catalysts, such as bismuth octoate. Since the use of these catalysts increases the VOC value of the obtained polyurethane material, they should be used only in sufficiently small quantities, i.e., in such quantities that the VOC value remains below the prescribed maximum value. In some cases, it has been shown that the use of an organobismuth catalyst of formula (I) is not essential and that the required catalytic effect is particularly obtained by a combination of an organotin catalyst and a small amount of an organobismuth catalyst that releases volatile compounds without exceeding the permitted VOC value.

Organotin catalyst

The organotin catalyst used in the favorable implementation of the process of this invention corresponds to the following general formula (II):

[image]

to the following general formula (III):

[image]

or the following general formula (IV)

[image]

where is

R1 C1-C8 alkyl group, a

R2 is either:

a linear or branched C13-C19 alkyl or alkenyl group, or

a linear or branched C1-C19 alkyl or alkenyl group, preferably a C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups.

Compared to the organotin catalyst dimethyltin decanoate, the above organotin catalysts produce much less volatile compounds in the polyurethane material. This is either due to the fact that the carboxylic acid obtained when the catalyst is hydrolyzed is less volatile because it has a higher molecular weight, or due to the fact that this carboxylic acid is substituted with a group reactive with isocyanate, so that it is chemically bound in the polyurethane matrix. In the case of such substituted carboxyl groups, the R2 group has a lower molecular weight. Preferably, the R2 group is a C7-C19 alkyl or alkenyl group.

Since groups reactive with isocyanate on the catalyst compound cause a decrease in catalytic activity by binding the catalyst to the polyurethane matrix, it is advantageous to use an organotin catalyst of the formula (II), (III) or (IV) where R2 is a C13-C19 alkyl or alkenyl group that is not substituted by a reactive group with isocyanate. It is further advantageous that the R 2 group is linear.

In the process of the invention, it is advantageous to use the tin catalyst of formula (II). It was found that organotin catalysts of formula (III) are indeed more sensitive to hydrolysis than organotin catalysts of formula (II). In addition, organotin (IV) catalysts have been found to be more effective than the organotin (II) catalysts used, for example, in the processes described in US-B-6,194,475, although such organotin catalysts, particularly tin ricinoleate, are also used in process from this invention, especially when the main catalytic effect is provided by an organobismuth catalyst. Since the organotin catalysts of formula (II) are also quite sensitive to hydrolysis, it is advantageous to add them to the isocyanate mixture. Even in the isocyanate mixture, the organotin catalysts of formula (II) are subjected to hydrolysis, specifically, as a result of contact with moisture from the air. Considering this problem with hydrolysis, organotin catalysts, where the R2 group does not contain groups reactive with isocyanate, are particularly advantageous, because otherwise organotin catalysts would react already in the isocyanate mixture or would be added to the polyol mixture, where they are even more subject to hydrolysis.

It is advantageous if R2 is a C15-C19 alkyl or alkenyl group, given the lower vapor pressure of high molecular weight carboxylic acids, which results in a lower VOC value. It is further preferred that the R 2 groups are alkenyl groups. The presence of one or more double bonds actually lowers the melting point of the catalyst so that, even with a higher molecular weight, the catalyst is added in liquid form to the polyurethane system. Considering the fact that they combine relatively high molecular weights with a relatively low melting point, oleyl groups, linoleyl groups, linolenyl groups or their combinations are most advantageous as R2COO-groups in formulas (II) and (III) of the organotin catalyst.

It is advantageous that the alkyl group R1 is a C1-C4 alkyl group, most advantageously a methyl group, given the higher reactivity of such catalysts.

The most favorable organotin catalysts are dialkyltin dioleates, especially dimethyltin dioleates, where a small part of the carboxylate groups are linoleate and linolenate groups due to the use of natural oils for the production of this organotin catalyst.

When the reactive mixture is processed for spray application, the organotin catalyst is usually used in such an amount that the resulting polyurethane material contains 200 to 1600 ppm, preferably 200 to 1000 ppm, of the element tin. When the reactive mixture is processed according to the reaction injection molding (RIM) process, the organotin catalyst is usually used in such an amount that the resulting polyurethane material contains 200 to 1600 ppm, preferably 300 to 1000 ppm, of the element tin.

The advantage of the advantageous embodiment, where the tin catalyst is used in combination with the bismuth catalyst, is that the tin catalyst ensures effective curing at the end of the polymerization reaction, thus reducing the time to curing. This advantage is more pronounced in the application of spray than in the application of RIM due to the lower temperature of the reactive polyurethane material at the end of the polymerization reaction, when the reactive mixture is applied by spray to the open surface of the mold.

Organozinc (II) catalyst

In a preferred embodiment of the process of this invention, an organozinc (II) catalyst is used. This organozinc catalyst specifically corresponds to the following general formula (V):

[image]

wherein R 2 is a C 1 to C 19 alkyl or alkenyl group, which is linear or branched and which is substituted or unsubstituted.

It is advantageous that R 2 is a C 1 to C 12 alkyl or alkenyl group, since these zinc catalysts are liquid, which is advantageous in view of their processability. Contrary to organobismuth and organotin catalysts, organozinc catalysts contain less free carboxylic acids and/or are more resistant to hydrolysis, so less free carboxylic acids are formed. The zinc catalyst, therefore, should contain carboxyl groups of lower molecular weight, i.e. a more volatile carboxylic acid. The use of zinc dioctoate is preferred.

According to this invention, it has been found that, contrary to aromatic elastomeric polyurethane systems and polyurethane foam systems, organozinc catalysts, as such, do not provide effective catalysis of polyurethane polymerization reactions of "non-aromatic" microcellular or acellular photostable polyurethane formulations. In accordance with the present invention, however, an organobismuth catalyst is primarily used to provide the required catalytic effect. It was found that, in combination with an organobismuth catalyst, an organozinc catalyst improves the catalytic effect of bismuth, so that, in fact, a synergistic effect is achieved when this combination of catalysts is used, especially when the organozinc catalyst is used in a relatively small amount compared to the amount of bismuth catalyst .

In the process of this invention, the organozinc catalyst is not really intended to provide a catalytic effect, but it was found that the organozinc catalyst competes in the initial phase of the reaction with the organobismuth catalyst and that the unfavorable rapid increase in viscosity, caused by the organobismuth catalyst, is avoided in this way or at least reduced. This effect is achieved when the catalyst component contains an organobismuth and organozinc catalyst whose elemental bismuth/elemental zinc ratio is greater than 8/1, preferably greater than 9/1, when the reactive mixture is applied by spray. When the reactive mixture is applied by the RIM process, where the reaction usually takes place at a higher temperature, more zinc catalyst is needed to prevent too rapid an increase in viscosity. A further difference compared to the RIM process is that in the spray process, a faster initial increase in viscosity is desirable so that the reaction mixture does not leak out. In the case of spray application, the catalyst component therefore contains an organobismuth and organozinc catalyst whose elemental bismuth/elemental zinc ratio is greater than 4/1, preferably greater than 5/1. In both applications, the use of larger amounts of organozinc catalyst is not favorable due to the negative the effect that such larger quantities have on the rate of curing.

In one advantageous embodiment of this invention, it is advantageous for the catalyst component to contain a combination of organobismuth, organotin and organozinc catalysts. Such a combination of catalysts achieves optimal catalysis without the use of a lead catalyst, where the organozinc catalyst ensures a slower initial increase in viscosity, while the organotin catalyst ensures good final curing, especially in spray applications.

Other catalysts

In the process of this invention, other catalysts can be used, provided that they do not form volatile compounds, or form only small amounts of volatile compounds in the polyurethane material. These other catalysts can, for example, be chosen from other organobismuth or organotin compounds mentioned in EP-B-0 379 246. They especially include zeolite type catalysts, which are described in this European patent and which do not produce volatile compounds. These catalysts are alkaline aluminum silicates with Na and/or K ions, where the favorable diameter of the micro-cavities is between 2 and 10 A, and typically between 3 and 4 A and to which the following general formula corresponds:

(M2O)a - (Al2O3)b - (SiO2)c - (H2O)d,

where M represents potassium and/or sodium. Along with potassium and/or sodium, calcium ions may also be present.

These silicates are mixed, as fine powders or as pastes, in a liquid dispersion medium with other reaction products to obtain polyurethane material.

As already stated earlier, it is advantageous that the alkaline catalysts described in EP-B-0 379 246 are not used, or only in a small amount, in the process of this invention, because they cause an increase in volatile compounds in the polyurethane material.

To reduce the VOC value of the obtained polyurethane material, it is advantageous to mix the isocyanate component and isocyanate-reactive components with each other in such amounts that the NCO-index (= number of NCO - groups x 100/number of isocyanate-reactive groups) is greater than 90 , preferably greater than 95 and most advantageously greater than or equal to 100. In the case of such high NCO-indexes, essentially no unreacted isocyanate-reactive groups, specifically, OH- groups, remain in the polyurethane material. When the NCO-index is greater than 100, there is an excess of NCO-groups, which, however, will react with water present in the polyol component or with moisture from the air, to make amines, which further react with free NCO-groups to make urea. Regardless of these further reactions, it is advantageous that the NCO-index is lower than 120, and most advantageously lower than 110. This choice of NCO-index results in an ideal polyurethane network, which has been found to reduce the formation of volatile compounds in polyurethane materials.

In addition to the previously described components, the reactive mixture contains other components, such as a small amount of physical or chemical growth agents, pigments, internal release agents, thixotropic thickening agents (for spray application), etc. The reactive mixture especially further contains antioxidants and/ or UV absorbers due to the increase in the photostability of the polyurethane material, with the fact that it is advantageous to use synergistic combinations of antioxidants, UV absorbers and HALS stabilizers (light stabilizers based on blocked amines).

Examples

The following starting materials were used in the examples:

Polyol: an addition product of glycerin, propylene oxide and ethylene oxide, which has a hydroxyl number of 36 and a primary OH content of at least 85% (POL);

Isocyanate: a mixture of isocyanate trimers and isocyanate monomers based on IPDI, with a terminal NCO content of 28% (in the case of S1-S5, R4-R6) and a terminal NCO content of 30% (in the case of R1-R3) (ISO);

Chain-extending component: ethylene glycol (EG);

Cross-linking component: diethanolamine (DEOA);

Antioxidants / UV absorbers: synergistic mixture (AO/UV) of equal parts by weight:

- ethylene bis(oxyethylene)bis[3-(5-tert.butyl-4-hydroxy-m-tolyl) propionate];

- 2-(2-hydroxy-3,5-di-tert.amyl-phenyl)-2H-benzotriazole and

- bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate

Zeolite-type catalyst: sodium aluminum silicate - 3A, dispersed in polyol (ZC);

Thixotropic agents: fumed silicon dioxide (TX);

Pigments: dispersion of carbon black, titanium dioxide and isoindolinone in polyol for samples S1 to S5 and samples R1 to R3; black coal dispersion for samples R4-R7 (CP);

Bi-catalyst: BC1: Bismuth octoate with 24% Bi;

BC2: Bismuth neodecanoate with 17% Bi;

BC3: Bismuth oleate with 20% Bi;

Sn-catalyst: TC1: Dimethylcositardineodecanoate with 23% Sn;

TC2 : Dimethyl tin diolate with 17% Sn;

TC3: Cotin 1707, a Caschem product, that is, a liquid organotin carboxylate catalyst with hydroxyl functionality in the carboxyl chain and 12.5% Sn;

Zn-catalyst: Zinc octoate (ZNC) with 23% Zn

The above components are mixed into two mixtures, that is, a polyol mixture containing a polyol, a chain-extending component, a chain-crosslinking component, an AO/UV absorber mixture, pigments, a zeolite-type catalyst, and BC1, BC2, BC3, TC3 and/or or ZNC and an isocyanate mixture containing an isocyanate and a thixotropic agent and, when used, TC1 and/or TC2.

1. Samples applied by spray (S1-S5) The conditions of technological processing in these samples are as follows:

raw material temperature:

25°C in the tank

65 °C in the mixer/injector

nickel-galvano mold surface temperature: 65°C output

components: 14 g/s

thickness of the layer applied by spray: about 1 mm

external release agent: emulsion of paraffin waxes in water.

2. Patterns ROME

A. Samples RIM R1 to R3 were processed under the following conditions:

raw material temperature: 45°C

nickel-galvano mold surface temperature: 80°C

component output: 100 g/s

layer thickness: about 2 mm

external release agent: dispersion of paraffin waxes in mineral alcohols.

B. Samples RIM R4 - R7 were processed under the following conditions:

raw material temperature: 45°C

steel mold temperature: 105°C

output of components: 200g/s

layer thickness: about 3 mm

external release agent: dispersion of paraffin waxes in mineral alcohols.

Handling of evaporation measurement samples

Evaporation measurements were performed on samples that were cured for 72 hours at 23°C/50% RH. The obtained samples are wrapped in aluminum foil (2 layers) and then packed in a synthetic foil or a slightly leaky bag (such as polyethylene, a freezer bag). The foil or bag is closed with Tesafilm.

The packed samples were frozen at -18°C until the day of analysis. The packaged samples were then warmed to room temperature, unpacked and analyzed according to Daimler Chrysler test procedure PB VWT 709.

Table 1: Formulations from examples and evaporation values of obtained polyurethane materials.

[image]

In the above table, more specifically, when S1 and S2 are compared, first of all it can be seen that the catalytic effect achieved by bismutholeate is essentially the same as the catalytic effect of bismuth octoate (for the same amount of element Bi), despite the possible steric hindrance of the higher molecular weight carboxyl group . This is probably due to the reduced susceptibility of bismutoleate to hydrolysis.

When SI and S2 are compared, it is further seen that when bismuth octoate is replaced by bismutholeate, a significant reduction in VOC value is obtained. Further reductions are obtained by replacing the tin catalyst dimethyltinideodecanoate (TC1) with tin catalyst dimethyltindioleate or Cotin 1707 (see S2-S4), more specifically, reducing VOC values well below the 100 ppm limit.

When S5 and S3 are compared, it can be seen that, by using a small amount of organozinc catalyst in combination with an organobismuth catalyst (elemental bismuth/elemental zinc ratio = 9.6/1), the time to cure is reduced.

Samples RIM R1 and R2 show that the same catalytic effect is obtained when the tin catalyst dimethyldinodecanoate is replaced by dimethyltin diolate, although about 5 times the amount of catalyst is required. Samples RIM R2 and R3, on the other hand, show again that the replacement of bismuth octoate with bismuth oleate does not require an additional amount of catalyst.

From the RIM R2 sample, it appears that when a sufficiently large amount of organotin catalyst is used, the amount of organobismuth catalyst is reduced to such a value that, for example, the common bismuth octoate catalyst is used without the evaporation values being too high. A further significant reduction in evaporation value is obtained by replacing bismuth octoate with bismuth oleate, as shown in example R3.

Samples RIM R5 and R6 show that for RIM applications, a short time to solidification is achieved by using a bismuth catalyst either in combination with an organotin or an organozinc catalyst, where the organozinc catalyst is used only in a small amount of 0.25 parts by weight of the element Zn part of the element Bi (i.e. ratio elemental bismuth/elemental zinc = 4/1). When R6 is compared to R7, it can be seen that, with a relatively small amount of organozinc catalyst, the time to cure is significantly reduced compared to the formulation where only bismuth is used as a catalyst. When operating at a sufficiently high molding temperature, short time to solidification is achieved in RIM applications by combining an organobismuth and organozinc catalyst, without the use of a tin catalyst.

Claims (29)

1. The process, characterized by the fact that it contains the process of producing a microcellular or non-cellular photostable polyurethane material with a density greater than 500 kg/m3, especially greater than 700 kg/m3, in which the reactive mixture of polyurethane precursors is left to react to obtain a polyurethane material, where it is reactive a mixture composed of components containing at least: A) an isocyanate component consisting of at least one isocyanate compound, which has at least two NCO groups that are not directly attached to an aromatic group; B) isocyanate-reactive components they contain b1) a component containing active hydrogen composed of at least one compound containing active hydrogen and having: functional groups containing primary and/or secondary OH- groups, NH- groups and/or NH2- groups; a nominal functionality of 2 to 8 and an equivalent weight of between 100 and 4000, preferably between 800 and 2000; b2) from about 0 to about 30 parts, preferably from about 2 to about 30 parts, per 100 parts of components b1, b2 and b3, a component that extends the chains and/or a component that crosslinks them, consisting of at least one compound that lengthens the chains and/or at least one compound that cross-links them and which has an equivalent weight of less than 100, whose functional groups are OH-groups, of which at least 50% are primary OH-groups and whose functionality is from 2 to 6; you b3) amine-initiator component that forms a co-catalytic system with catalyst component C and which is composed of at least one amine initiator whose functionality is from 2 to 6 and equivalent weight is less than or equal to 200 and which contains at least one aliphatic or alicyclic NH2- or NH- group; you C) a catalyst component that is essentially lead-free and that contains at least one organobismuth (III) catalyst, and said organobismuth catalyst contains at least one organobismuth (III) catalyst corresponding to the following formula (I): [image] where is m = 0-2 p = 1-3 m + p = 3 R1 is a C1-C8 alkyl group, a R2 is either a linear or branched C13-C19 alkyl or alkenyl group, or a linear or branched C1-C19 alkyl or alkenyl group, preferably a C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups, and/or the said catalyst component contains, in addition to the said organobismuth catalyst, at least one organotin (II or IV) catalyst, to which the following formula (II) corresponds: [image] the following formula (III): [image] or the following formula (IV): [image] where R1 is a C1-C8 alkyl group and R2 is either a linear or branched C13-C19 alkyl or alkenyl group, or linear or branched C1-C19 alkyl or alkenyl group, preferably C7-C19 alkyl or alkenyl group, substituted by at least one group reactive with isocyanate, especially one or more OH-, NH- and/or NH2- groups, where the components of the reactive mixture are further selected in such a way that the resulting polyurethane material has a VOC value, measured in accordance with the Daimler Chrysler PB VWT 709 standard, lower than 250 ppm, preferably lower than 150 ppm and most preferably lower than or equal to 100 ppm. 2. The process according to claim 1, characterized by the fact that it uses an organobismuth catalyst of the formula (I). 3. The method according to claim 1 or 2, characterized in that it uses an organobismuth catalyst of the formula (I), where m = 1 or 2 and where R1 is a C1-C4 alkyl group. 4. The process according to any one of claims 1 to 3, characterized in that it uses an organobismuth catalyst of formula (I), where m = 0. 5. The process according to any one of claims 1 to 4, characterized in that it uses an organobismuth catalyst of formula (I), where R2 is a C15-C19 alkenyl group. 6. The process according to any one of claims 1 to 5, characterized in that it uses an organobismuth catalyst of formula (I), where R2 is a C13-C19 alkenyl group. 7. The method according to claim 6, characterized in that it uses an organobismuth catalyst of the formula (I), where the R2COO- groups are oleyl groups, linoleyl groups and/or linolenyl groups. 8. The process according to any one of claims 1 to 6, characterized in that it uses an organobismuth catalyst of the formula (I), where R2 is a C13-C19 alkyl or alkenyl group which is not substituted by an isocyanate-reactive group and which is preferably linear. 9. The method according to any one of claims 1 to 8, indicated by the fact that said reactive mixture was applied by spray on the surface of the mold, in which case the organobismuth catalyst is used in an amount of between 150 and 850 ppm, preferably between 150 and 600 ppm of the bismuth element in the obtained polyurethane material, either injected into a closed mold, according to the reaction injection molding (RIM) process, in which case the organobismuth catalyst is used in an amount of between 250 and 2500 ppm, preferably between 800 and 1650 ppm of the bismuth element in the obtained polyurethane the material. 10. The method according to any one of claims 1 to 9, characterized in that it uses an organotin catalyst of the formula (II), (III) or (IV), preferably an organotin catalyst of the formula (II). 11. The method according to claim 10, characterized in that it uses an organotin catalyst of the formula (II) or (111), where R1 is a C1-C4 alkyl group, preferably a methyl group. 12. The process according to claim 10 or 11, characterized in that it uses an organotin catalyst of the formula (II), (III) or (IV), where R2 is a C15-C19 alkyl or alkenyl group. 13. The process according to any one of claims 10 to 12, characterized in that it uses an organotin catalyst of formula (II), (III) or (IV), where R2 is a C13-C19 alkenyl group. 14. The method according to claim 13, characterized in that it uses an organotin catalyst of the formula (II), (III) or (IV), where the R2COO- groups are oleyl groups, linoleyl groups and/or linolenyl groups. 15. The process according to any one of claims 10 to 13, characterized in that it uses an organotin catalyst of the formula (II), (III) or (IV), where R2 is a C13-C19 alkyl or alkenyl group that is not substituted with an isocyanate-reactive group and which is preferably linear. 16. The method according to any one of claims 10 to 15, characterized in that the said reactive mixture was applied by spray to the surface of the mold, in which case the organotin catalyst is used in an amount of between 200 and 1600 ppm, preferably between 200 and 1000 ppm of the tin element in the obtained polyurethane material, either injected into a closed mold, according to the process of reaction injection molding (RIM), in which case the organotin catalyst is used in an amount of between 200 and 1600 ppm, preferably between 300 and 1000 ppm of the tin element in the obtained polyurethane material . 17. The method according to any one of claims 1 to 16, characterized in that said catalyst component further contains an organozinc (II) catalyst. 18. The method according to claim 17, characterized in that it uses an organozinc catalyst corresponding to the following formula (V): [image] where R 2 is a C 1 to C 19 , preferably a C 1 to C 12 alkyl or alkenyl group, which is linear or branched and which is substituted or unsubstituted. 19. The method according to claim 18, characterized in that it uses zinc dioctoate as said organozinc catalyst. 20. The method according to any one of claims 17 to 19, characterized in that the catalyst component contains an organobismuth and organozinc catalyst where the ratio elemental bismuth/elemental zinc is greater than 8/1, preferably greater than 9/1, when the reactive mixture is applied by spray or greater than 4/1, preferably greater than 5/1, when the reactive mixture is applied by the RIM process. 21. The method according to any of claims 17 to 20, characterized in that the catalyst component further contains an organotin catalyst as defined in any of claims 9 to 16, especially when the reactive mixture is applied by spray. 22. The method according to any one of claims 1 to 21, characterized in that the active hydrogen-containing component is essentially BHT-free or contains at most 50 ppm BHT. 23. The process according to any one of claims 1 to 22, characterized in that said isocyanate component and said isocyanate-reactive components are allowed to react to an NCO-index greater than 90, preferably greater than 95 and, most advantageously, greater than or equal to 100, where it is advantageous for the NCO-index to be less than 120 and, most advantageously, less than 110. 24. Microcellular or non-cellular photostable polyurethane material, indicated by the fact that it has a density greater than 500 kg/m3, in particular greater than 700 kg/m3, which is obtained by allowing a reactive mixture of polyurethane precursors to react to give a polyurethane material, where the reactive mixture consists of components containing at least: A) an isocyanate component consisting of at least one isocyanate compound, which has at least two NCO groups that are not directly attached to an aromatic group; B) isocyanate-reactive components they contain b1) a component containing active hydrogen composed of at least one compound containing active hydrogen and having: functional groups containing primary and/or secondary OH- groups, NH- groups and/or NH2- groups; nominal functionality from 2 to 8 i an equivalent weight of between 100 and 4000, preferably between 800 and 2000; b2) from about 0 to about 30 parts, preferably from about 2 to about 30 parts, per 100 parts of components b1, b2 and b3, a component that extends the chains and/or a component that crosslinks them, consisting of at least one compound that lengthens the chains and/or at least one compound that cross-links them and which has an equivalent weight of less than 100, whose functional groups are OH-groups, of which at least 50% are primary OH-groups and whose functionality is from 2 to 6; you b3) amino-initiator component that forms a co-catalytic system with catalyst component C and which is composed of at least one amine initiator whose functionality is from 2 to 6 and equivalent weight is less than or equal to 200 and which contains at least one aliphatic or alicyclic NH2- or NH- group; you C) a catalyst component that is essentially lead-free and that contains at least one organobismuth (III) catalyst, and that the polyurethane material has a VOC value, measured in accordance with the Daimler Chrysler PB VWT 709 standard, lower than 250 ppm, preferably lower than 150 ppm and most preferably lower than or equal to 100 ppm, in which said organobismuth catalyst contains at least one organobismuth (III) catalyst corresponding to the following formula (I): [image] where is m = 0-2 p=1-3 m + p = 3 R1 is a C1-C8 alkyl group, a R2 is either a linear or branched C13-C19 alkyl or alkenyl group, or a linear or branched C1-C19 alkyl or alkenyl group, preferably a C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups, and/or the catalyst component contains, in addition to the mentioned organobismuth catalyst, at least one organotin (II or IV) catalyst, to which the following formula (II) corresponds: [image] the following formula (III): [image] or the following formula (IV): [image] where is R1 C1-C8 alkyl group, a R2 is either a linear or branched C13-C19 alkyl or alkenyl group, or a linear or branched C1-C19 alkyl or alkenyl group, preferably a C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups. 25. Polyurethane material according to claim 24, characterized in that it is produced according to the process as defined in any of claims 1 to 23. 26. Use of an organobismuth (III) catalyst, indicated by the following formula (I): [image] where is m = 0-2 p=1-3 m + p = 3 R1 is a C1-C8 alkyl group, a R2 is either a linear or branched C13-C19 alkyl or alkenyl group, or linear or branched C1-C19 alkyl or alkenyl group, preferably C7-C19 alkyl or alkenyl group, substituted by at least one group reactive with isocyanate, especially one or more OH-, NH- and/or NH2- groups, and/or organotin (II or IV) catalyst, to which the following formula (II) corresponds: [image] the following formula (III): [image] or the following formula (IV): [image] where is R1 is a C1-C8 alkyl group, a R2 is either a linear or branched C13-C19 alkyl or alkenyl group, or linear or branched C1-C19 alkyl or alkenyl group, preferably C7-C19 alkyl or alkenyl group, substituted by at least one isocyanate-reactive group, especially one or more OH-, NH- and/or NH2- groups in the production of microcellular or non-cellular photostable polyurethane material having a density greater than 500 kg/m3, especially greater than 700 kg/m3, to preserve the VOC value of the obtained polyurethane material, measured in accordance with Daimler Chrysler's PB VWT 709 standard, below 250 ppm, preferably below 150 ppm, and most preferably below or equal to 100 ppm, essentially without the use of an organolead catalyst. 27. Use according to claim 26, characterized in that it uses an organobismuth catalyst having the properties defined in any of claims 2 to 9. 28. Use according to claim 26 or 27, characterized in that it uses an organotin catalyst having the properties defined in any of claims 10 to 16. 29. Use according to any one of claims 26 to 28, characterized in that it further uses an organozinc (II) catalyst which in particular has the properties defined in any one of claims 18 to 20.